Earth Is Not The Only Planet In The Solar System That Sees Total Solar Eclipses

Earth is not the only place to see a total solar eclipse. Credit: Shutterstock

Eclipse-chasers often spend thousands of dollars traveling across the world to stand under the moon’s shadow to experience totality. So what do you do when you’ve seen the dazzling solar corona dozens of times? You go hunting for eclipses on other planets, that’s what.

Last weekend at the Solar Eclipse Conference 2018 in Genk, Belgium, Jamaica-based computer programmer and eclipse-chaser Bill Kramer presented the results of his study into a simple question: is the Earth the only planet in our solar system to enjoy a perfect eclipse alignment?

'If someone says that Earth is the only place to see a total solar eclipse, well, that’s actually not true,' said Kramer.

Kramer, who’s seen 17 total solar eclipses so far, studied 141 moons around Earth, Mars, Jupiter, Saturn, Uranus and Neptune (the inner planets Mercury and Venus have no moons). 'A good eclipse is a perfect fit, when the size of the sun and moon are roughly equal,' explained Kramer. 'It should be total or annular as viewed from the planet.'

The sun is obscured by the moon during an annular solar eclipse in Tokyo, Japan. Photographer: Tomohiro Ohsumi/Bloomberg

While a total solar eclipse is where the moon completely covers the solar disk, an annular eclipse is a type of partial eclipse, where the moon is too small to cover the solar disk, instead producing a so-called 'ring of fire'. The next annular solar eclipse on Earth will occur on 26 December, 2019, which is most likely to occur in clear skies from southern India.

Kramer first pulled data on moons down from NASA, then developed a computer program to compare just their angular sizes at the extremes of their orbits. 'I was not looking at detailed circumstances, just a simple comparison,' said Kramer, who looked at the distance of the sun at perihelion (the point in planet's orbit nearest to the sun) and aphelion (furthest) to determine the maximum and minimum sizes would appear. He then added the data for each moon at periapsis (nearest to the body that it orbits) and apoapsis (furthest) and looked at the range. Divide one by the other and you get a size ratio. 'A ratio of greater than 1 means an annular eclipse event, and a ratio of less than one means a total eclipse event,' explained Kramer.

On Earth, the ratio is between 0.940 and 1.104, which explains why we see such fantastic solar eclipses; it's an almost perfect fit. Kramer found that 31 moons in the solar system caused extreme total eclipses, when the Sun is completely covered, and 107 extreme annular eclipses where the Sun is visible around a moon. 'It’s more common to see an annular eclipse than a total eclipse in our solar system,' he said. 'But I found three of them where annular and total solar eclipses are possible.'

Kramer discovered that other than Earth, it's at Saturn that the next best eclipses might be visible. 'I found Earth-like eclipse conditions for Epimetheus and Pandora,' he said.

However, these are no easy eclipses. Pandora is a an oblong-shaped, 50-mile diameter moon that takes just 15-hours to orbit Saturn. 'It’s not a good fit. We would never see a very good eclipse even in the total phase because the sun would always be shining through,' said Kramer. 'But you might see a double diamond ring for a fraction of a second.'

A diamond ring is most easily seen at the end of a total solar eclipse on Earth, when totality ends as the first beads of sunlight coming through the moon’s mountains coalesce into a brief but beautiful burst of sunlight. For a split-second it looks like the jewel on a ring around the moon.

Epimetheus could produce a total solar eclipse most similar to that seen from Earth. Credit: NASA/JPL-Caltech/Space Science InstituteNASA/JPL-Caltech/Space Science Institute

It's Epimetheus that creates a solar eclipse that most resembles those seen from Earth. The potato-shaped moon, just 72 miles in diameter, takes 17 hours to go around Saturn. That means another super-short eclipse. From when Epimetheus begins to cover the sun to when it departs would last a mere 15 seconds. 'The computation would have to be very precise to be in the right location to see it,' said Kramer.

Kramer calculated the observation conditions from the cloud tops of Saturn and Jupiter because these gas giants have no defined surface. However, since the moons orbit so quickly, you could get another eclipse very soon after. 'You would have to reposition yourself on the planet … but since you’re already traveling above the surface of the clouds, how hard is it to take your rocket and catch-up with it?' joked Kramer. 'That’s a whole new definition of eclipse-chasing.'

Although three moons cause total eclipses in the solar system, Earth's Moon does it best. Credit: Shutterstock

However, the title of 'best eclipse' was easy. 'Of the 141 moons I tested, 22% were total eclipses only, 76% were annular eclipses only, 6% were interesting,' said Kramer. 'And only one is the best.'

I have been a science and travel journalist for 20+ years. I have made it my business to get to know nature and the night sky. Want to know the best week to go stargazing? When and where you can see the Milky Way? Or when the next eclipse is? I can help. I love to travel, us...